Abstract
The acute phase response (APR) is part of the early defense system after triggers from trauma, infection, stress, neoplasia, and inflammation.4,8 A primary goal of the APR is to reestablish homeostasis and initiate healing. More than 200 acute phase proteins (APP) have been identified as participants in the APR.7 Some APP such as albumin decrease with inflammatory processes and are known as negative APP. Others increase from 2- to 100-fold and are known as minor, moderate, or major APP. These may be part of the acute process while others dominate chronic inflammatory processes.
Protein electrophoresis (EPH) has been used for many years in avian and wildlife medicine to monitor the APR.2,3,10,11 While not quantitative of single proteins other than albumin, the method does provide quantitation for groups of APP in alpha, beta, and gamma globulin fractions. As with EPH, assessment of individual APP have been demonstrated to have a differential sensitivity for the inflammatory process (i.e., vs fibrinogen, total WBC).2,8 For humans and some animal species, assays for specific APP have been implemented and have demonstrated the increased level of sensitivity for prognostic use as EPH may quantitate at the level of mg/ml level vs APP assay quantitation at the ng/ml level. Automated assays as well as expensive and labor intensive ELISA-based methods have been implemented especially for use with equine and canine samples.6,9 Recently, a paper was published indicating the possible application of these assays for use in different wildlife species.1 The goal of the current study is to validate and examine the cross-reactivity of reagents in an automated platform for use with variety of wildlife and avian samples, as well as seek their specific application as a diagnostic and/or prognostic marker in specific disease states.
The assays selected for review include serum amyloid A (SAA), C reactive protein (CRP), and haptoglobin (HP). SAA is considered a major APP of equine species and CRP is considered a major APP of canine species (and humans).4,8 Haptoglobin is often considered to be a minor APP, but it has an important role in chronic inflammatory processes in many species.4 Preliminary studies have indicated SAA to be a clinically valuable analyte in manatees with cold stress and trauma where values ranged from 81 to 2438 mg/L versus normal manatees with SAA <20 mg/L. Paired determinations were used in several animals and they revealed a progression to normality with positive response to rehabilitation efforts. SAA values were within normal limits as with other clinical indicators at the time of release. These results are consistent with those previously published with ELISA methods.5 Our work with other marine mammal samples (dolphins, beluga whales) indicates potential utility of both SAA and HP. In elephants, SAA and HP appear to be primary APP with normal values of <20 mg/L and 1 mg/ml, respectively. Preliminary studies using banked serum from EEHV infected elephants showed promise with correlation with viremia with a maximum 5-fold increase in SAA and HP in samples from some animals.
Lastly, other preliminary studies have examined APP in a variety of avian species and small exotic animals. In birds, transferrin and SAA appear to have moderate to major function in APR. An HP counterpart (PIT54) was also detectable in samples from many birds that were suffering from infectious disease including aspergillosis. Transferrin increases were observed in samples from egg laying birds. Interestingly, however, APP increases were not consistently observed in those samples with abnormal EPH, which indicates that there may be other major APP to quantitate in avian species. These preliminary studies corroborate the initial findings of Bertelsen and coworkers that there is a venue for the application of APP assays in wildlife medicine. Additional studies are underway to examine these findings further, as well as to document disease models in other species.
Acknowledgments
The authors thank the Houston Zoo and the St. Louis Zoo for their contributions to the study involving elephant samples, the Miami Seaquarium and the Georgia Aquarium for their contributions to the studies involving samples from marine mammals, and the White Oak Conservation Center for their contributions to the studies involving samples from rhinos and other wildflife species.
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